Civic EG

I have a d16y7... anyone know why I'm only getting about 20 MPG?!?! This is while driving normal as well...[/list]

Do you have a check engine light on?

Here's a similar thread with some possible solutions listed:
http://www.civic-eg.com/viewtopic.php?t=22933

Every once in a while it will while idling

I was looking at the thread you posted and I noticed bout the black smoke and black stain on bumper... mine does have that... am I supposed to have a second o2 sensor on the cat? Cuz I only have 1 on the headers

There are a few things you need to check out or just replace. And no there should be no O2 behind the cat. only 96-up cars or obd-II cars have 2 O2 sensors.

First thing to check out is your spark plugs, if they look really black or if you are unsure of the last time that they were replaced be a good start. Doing a tune up on the engine helps a lot so spark plugs, wires cap and rotor. Ensures you get enough spark and combustion is taken place properly.

Next is the Fuel filter, if you don't when it was last replaced just replace it. As time goes on it collects stuff and cleans the fuel you put in your car correct, well after time it will build up and create more pressure in your fuel system which causes you to run rich.

After that you could have spray some throttle body cleaner threw the throttle body and it will clean your intake and throttle body.

Also general maintenance like your valve lash adjustment, timing belt. oil changes, trans mission fluid etc. But you should be getting upward of 30 mpg

Thanks I'll have to check all that out

Also check that engine code and it will tell you the problem.

Here's a thread on how to do that:

http://civic-eg.com/viewtopic.php?t=1558